21975156 has 144 divisors (see below), whose sum is σ = 68490240. Its totient is φ = 5806080.

The previous prime is 21975137. The next prime is 21975157. The reversal of 21975156 is 65157912.

21975156 = 204² + 205² + ... + 420².

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21975156.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21975157) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 226500 + ... + 226596.

Almost surely, 2^21975156 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21975156, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34245120).

21975156 is an abundant number, since it is smaller than the sum of its proper divisors (46515084).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21975156 is a wasteful number, since it uses less digits than its factorization.

21975156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174 (or 169 counting only the distinct ones).

The product of its digits is 18900, while the sum is 36.

The square root of 21975156 is about 4687.7666324168. The cubic root of 21975156 is about 280.0984177838.

The spelling of 21975156 in words is "twenty-one million, nine hundred seventy-five thousand, one hundred fifty-six".